1. Field
One or more embodiments of the present teachings relate to a composite anode active material, an anode including the composite anode active material, a lithium battery employing the anode, and a method of preparing the composite anode active material.
2. Description of the Related Art
Carbonaceous materials such as graphite are representative examples of anode active materials for lithium batteries. Graphite has excellent electrical capacity retention characteristics and excellent voltage characteristics. In addition, graphite does not vary in volume when used to form an alloy with lithium, and thus, may increase the stability of a battery. Graphite has a theoretical electrical capacity of about 372 mAh/g and a high irreversible capacity.
In addition, metals capable of forming alloys with lithium may be used as an anode active material for lithium batteries. Examples of metals capable of forming alloys with lithium include silicon (Si), tin (Sn), aluminum (Al), and the like. These metals have a very high electrical capacity. For example, these metals may have an electrical capacity that is 10 times higher than that of graphite. Such metals undergo a change in volume during charging and discharging, thereby electrically isolating the active material within the electrode. In addition, an electrolyte decomposition reaction becomes severe, due to an increase in specific surface area of the active material. Si also has a relatively high resistance.
Metals capable of forming alloys with lithium may be formed into composites with carbonaceous materials, in order to suppress volumetric expansion and improve conductivity. However, conventional examples of such composite materials rely only on Van der Waals forces for cohesion, and thus, the metal and the carbonaceous material are easily separated during charging and discharging. Thus, there is a demand for a high-capacity and long-lifespan active material for high-capacity lithium batteries.